Ignition system



May 9, 1950 T. P. GlBLlN IGNITION SYSTEM Filed 001'.. 15, 1,948

2 Sheets-Sheet 1 fly'. 1

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May 9, 1950 T. P. GIBLIN 2,506,664

IGNITION SYSTEM Filed Oct. l5, 1948 2 Sheets-Sheet 2 Patented May 9, 1950 asas-t4 IGNITION SYS TEM Thomas P. Giblin, Pawtucket, R. I., assignor to G. A. Swanson Engineering Co., West Warwick, R. I., a corporation of Rhode Island Application October 15, 1948, Serial No. 54,765

3 Claims.

My invention relates to ignition systems employed in conjunction with internal combustion engines.

A constant source of trouble encountered in the course of operating internal combustion engines resides in the fouling of the spark plugs. In the course of time suicient carbon is deposited adjacent the terminals to form a relatively low resistance path shunted across the spark gap. When that happens the firing charge leaks through the carbon without effecting an igniting spark for the explosive mixture in the cylinder. Although it has been proposed to overcome this diilculty by incorporating an energy storage device in the circuit, no practically satisfactory solution of the problem has yet been presented.

The most important object of my invention is to improve the eiiciency and reliability of ignition systems for internal combustion engines.

Another object of the invention is to improve ignition systems for internal combustion engines and specifically to prevent the fouling of the spark plugs.

In one aspect my invention comprises an improved circuit for the ignition system of an internal combustion engine, while in another aspect my invention comprises a compact unit containing most of the elements of the circuit and adapted for installation on existing ignition systems of conventional design.

An important feature of the invention resides in the combination of a condenser, a spark gap and a choke coil connected between the transformer and the spark plug and arranged always to provide a fat spark at the spark plug terminals, regardless of the condition of the plug.

These and other objects and features of the invention will be more readily understood and appreciated from the following detailed description of a preferred embodiment thereof selected for purposes of illustration and shown in the accompanying drawings, in which:

Fig. 1 is a schematic circuit diagram embodying my invention as applied to a single spark plug,

Fig. 2 is a schematic circuit diagram illustrating the application of the principles of the invention to a plurality of spark plugs,

Fig. 3 is a view in transverse cross section through the condenser along the line 3 3. of Fig. 5,

Fig. 4 is a plan view of a unit constructed in accordance with the invention,

Fig. 5 is a bottom plan view of the unit with the filling material removed to show the arrangement of the elements,

Fig. 6 is a view in side elevation of the unit, and

Fig. '7 is a wiring diagram of the elements of the unit of Figs. 3-6.

As shown in Fig. 1 the circuit of my invention is combined with a conventional transformer of the sort ordinarily used to provide high voltage impulses to the spark plugs of an internal combustion engine. The transformer I9 is shown in longitudinal cross section and includes a core Il formed of a bundle of soft iron wires. The primary of the transformer comprises a relatively small number of turns of relatively heavy gauge wire I2, while the secondary consists of a relatively large number of turns of smaller gauge wire le, coiled as a plurality of concentric helices separated by layers of insulating material such as -glassine paper. The secondary is formed as two spaced coils connected in series as shown at I8. One side of the primary coil I2 is provided with a lead wire 20 connected to ground through a cable 24 to which one side of the secondary coil i4 is also connected by means of a lead wire 22. The other side of the primary l 2 is connected through a lead wire IS to a source of low voltage pulses. The other side of the secondary I 4 is connected through a lead wire 26 to an air core choke coil 30 which in turn is connected to the positive side of a condenser 32 and to one side of an air gap 34. The other side of the air gap 34 is connected to center terminal of a conventional spark plug 36 which is grounded in the cylinder block of the engine. In order to show a complete circuit, however, a wire 38 is shown connected to the outside terminal of the spark plug and to ground. The negative side of the condenser 32 is also connected to ground.

I have found that a condenser having a capacity of the order of 0.01 mid. is suitable for my purpose and that the choke coil 3!) may conveniently comprise a 7.5 meter choke.

The circuit shown in Fig. 1 is novel in view of the inclusion of the choke coil 3D, since others have lproposed to place a condenser and an air gap between the secondary of the transformer and the spark plug. Considering the circuit without the choke 30, it becomes obvious that a pulse from the transformer will be stored in the condenser 32 until the voltage reaches a value suilicient to jump the gap 34, at which time a very sharp high voltage pulse is applied to the spark plug. A pulse of this character will'form a spark at the terminals of the plug regardless of the condition of the plug. That is to say, a very sharp high voltage pulse will jump across the air gap of the spark plug rather than traverse the low resistance path formed by deposited carbon. It might be thought that the circuit vwithout the choke coil would be adequate but I have found as the result of many tests that in the absence of the choke coil the engine willnot respond properly when the throttle is suddenly opened. A1- though an engine with fouled plugs will run smoothly at a steady rate, when the throttle is suddenly opened, the plugs will not fire properly and the engine will buck. However, when a.

choke coil is inserted between the secondary of the transformer and the condenser and air gap, the enginewill :respond smoothly.: as the throttle is opened 'and sudden changesv in'engine speed will have no effect on the ring of the spark plugs.

While I am not certain of the exact naturenoi y.prevented The-wavelength of .-the.- oscillations V:produced-in the circuit will.

-and lmeters; thereforaa 7.5,meter choke rep-Vv 20 having ordinarily liebetween resents a judicious compromise.

V'I'he ycircuit' shown .inlig 2.diiiers ffrom that .shown in Fig. lonlyby the inclusion of a distributor 40 connectedtothe junction `oifthe choke 30 .and the condenser 3?. and employed in .conjuncvtion with. four spark plugs 'infthe Vupper. porf., tion of each. offvvhich there is provided an air gap 1.42. .Ithas been proposed-to employ acondenser .and an air gap for eachspark plug in an internal .combustion .engine,.and it has been proposed also to employ asingle condenser` anda single airgap` to serve all thev spark plugs. I have found, however, .that while it is possible to obtain satisfactory results with a single condenser connected `as shown in Figs. land 2 the resultsare slightly improved if a separate airgap is, employed incon- .nection with each plug." Thei optimum combination is a single condenser anda plurality of'lair ...gaps connectedas'shown in Fig. 2. `.I'have :made many testsv of .the various combinations referred ,toandi'lnd .that for practical' purposes a'singleA condenser and a singleairgap will produce satis'- factory results at minimum costs.

Y In Figs. 3-6 I have shown a` compact self-con- .tained unit adapted formounting at a convenient location with respect to an internal combustion engine` of conventional design *and 'adapted to convert itr to embody my invention. To this 'end 'I providera shallow -rectangularcasing of insulatiingmaterial including a solid top wall lili and side Wallsfili Within the' casingthere is v`deiind a small square chamber formed by integral-wallsld jwhch also Vserve todene along narrowrectann gular chamber at eitherY y endY of Athe casing. 'Within one of the end chambers I'mount a choke n coil' 59,'whi1e'an air gapvr 52 is mounted at 'theoppositeend. AvThe air gap comprisesa pair ofopposed terminals encased in' porcelain and heldin position between .a pair of spring" clips. The gap *between 'the terminals is inthe' order of 01.064! .Y In the centersquare chamb'er'I dispose a condenser 5dv constructed asY best shown' in" Fig. 3

wherein -ve layersV 5@ of metal fil'are separated VVby foin glass plates' 58. -A wire 64 'is-3 connected Vto three alternate layers of foil 56 whilea wiref62 Formed. 'in-the top-wan it gofr -ithesasing'is a socket 12. QI also provide afbin'ding post Y14 set l" in the top wallof the casing connected at its lower Itis obvious pts end to the wire B4 of the condenser 54 and connected at its other end to a wire 16 leading to ...ground The .other .end offthe; choke 50 is connected `to .aibus'qbar 1li-which runsilongitudinally 5 along the interior of the casing and is connected cto the wire 62 from the condenser 54 and also to the other side of the air Ygap 52. The circuit conne'ctionsV are shown diagrammatically in Fig. 7. -The socket .isadaptedto receive a Vcable (not yl0l shown) leading to the secondary winding of the A'transformer while the socket 12 receives a cable (not shown) .which leads to the center terminal V`of the distributor.

In4 order that the unit of my invention may conveniently be mounted upon the inside of the .dashboard of. anautomobile or control board of aboat, I provide'arecess running along .the center of the top wall 44 and two side walls of thecasing, suitably dimensioned to, receive along strap' 801 .outturnedanges .82, at. each. end to. receiveboltsf by means of which theunit may. be secured indesiredposition. I- may Aalsoprovide a bottom strap 86 .which rrunsfalongfthe bottom of the'casing and actsas aclamp tohold the elements firmly in position. Howeverg'lv prferto ll the interiorY ofthe casing with asphalt, pitch, or other suitable materialwhich provides insula- .tion for Vthe elements within the casing and .also serves as a matrix holding them rmly in proper ..30 position.

Various modifications .of Ythe `4'embodiments herein 'shown willsuggest. vthemselves to'lthose skilled in theart; it is not intended, howeverto 'limit the invention tofthe'preferred embodiments .35 shown but rather togm'easure:itpin'termsof the appended claims." Having now "described and illustratedra'pref erred embodimentb my invention what' I claim as new and desire to'secure by Lettersf'Patent of 40 the 'United States'is: Y

l. An ignition circuit comprising aA` source" of electric ,energyincluding-af transformer, a spark gap,a spark plug connected iny series with said spark; gap, a capacitor connected iniparallel with said spark' gap and saidspark'plug, and'a choke connected in series'betweenthe `secondary ofA said transformerjand said gap;l plug, [and capacitor. 2. An ignition circuit comprising a'plur'alityof spark plugs, a spark gap connected in series with each sparkplug, a capacitor connected in parallel across. said gaps and plugs, a'sourceA of Velectric energy includingatransformer, and a-choke coil "connected in series between theisecondary of said Y 0o former, andi a g capacitorV connected betweenv vsaid gap andv said' vinducta'nce at ,one end Aand to ground at 'the other.i n

'f"`THOMS":P-. GIBLIN.

frannsncNonsiclrED n The. following. referencesare ,ci .record iniv the Vvnie of this patent:

l UNITED?- STATES. .PATENTS Number VName Y 'Date 1,370,077 Whisler .i Mar. 1,1921 2,276,966 "HansellvMar. 17,V 1942 Y 2,331,912 -I-Ioltl'iouse'Jr..y Get-19,1943 

